Pile driver drive cap

ABSTRACT

A water-cooled drive cap for use with pile driving machines which also includes a sensing construction actuatable either electrically or pneumatically to provide an indication of the condition of the pile head and thereby prevent overdriving thereof.

United States Patent Frederick Aug. 5, 1975 I PlLE DRIVER DRIVE CAP 1039.369 9/1912 Eichler 17311.11

1 1,883 010 10/1932 SherwoodWW i761 lm'enmrl Lemard Fredemk- Cresmew 2,722,266 11/1955 Kersten .7 297/1 Tern whlppzmy. NJ (l798l [22] Filed: Feb. 21. 1974 Primary Examiner-Ernest R. Purser [2]] Appl' No 4441688 Attorney, Agerzl, or FirmEdwin E1 Greigg Related U.S. Application Data [62] Division of Ser, No. 142.174 May 11. 1971. Put. N0v

3,8l7 O9l [52] US. Cl. 1, 173/131 [51] Int. Cl. EOZD 7/14 [58} Field of Search 173/80, l3]. 139; 73/82, 73/84; 61/537, 53.72; l8l/36 A; 297/l8t); 267/136-l4l [56] References Cited UNITED STATES PATENTS 886,l93 4/l908 De \Vitt 1 1 1 1 1 1 4 173/13] [57] ABSTRACT A water-cooled drive cap for use with pile driving muchines which also includes a sensing construction actuatable either electrically or pneumatically to provide an indication of the condition of the pile head and thereby prevent overdriving thereof.

9 Claims, 10 Drawing Figures PATENTEI] AUG 5 PATENTEDAUE 5l975 3.897. 835

PATENTED AUG 5 I975 SHEET FIG) FIOIO FILE DRIVER DRIVE CAP This is a division of application Ser. No. 142,174, filed May 11, 1971 and now U.S. Pat. No. 3,817,091.

This invention relates to drive cap construction used in connection with pile driving and more specifically to a new type of water cooled elastomer cushioned drive cap with means for sensing the force of each blow as the pile is driven to prevent damage to the pile head from overdriving.

BACKGROUND OF THE INVENTION Drive caps for pile drivers fit over the head of the pile and transmit the hammer blows evenly to the pile while at the same time maintaining the head of the pile in alignment with the hammer by guiding the head parallel to the leads frame and retaining the pile in a straight predetermined path. It is desirable that the drive cap be adaptable to many or all types and sizes of piles such as timber or wood pile, concrete pile, H-beams, pipe pile, fluted pile and the like, each being held properly centered on the driving axis. Further, as the pile is driven, the operator must be careful to control the force of the blows so as not to exceed the elastic limit of the pile material (overdriving) in order to minimize costly tip damage.

The continuous pounding of the hammer upon the drive cap produces heat from hysteresis in the cushioning material used to cushion the blows, which heretofore have been made of wood, thus causing charring and burning and consequent destruction and requiring frequent replacement at considerable cost, as well as delay in operations.

With present equipment after a pile is driven, its max imum static bearing load must then be determined by a dead load bearing test which is costly in both time and material. The drive cap described in the following specification therefore provides new and novel means for providing greater endurance for the cushioning material by reducing the heating effect of the elastomer pad, as well as establishing an accurate method of measuring the dynamic force of each blow thereon and also furnishing means for determining the equivalent static bearing capacity of the pile after it is driven.

OBJECTS OF THE INVENTION Accordingly, it is the principal object of the invention to provide a transducer that will measure the maximum threshold force from the hammer that can be applied to the pile without causing permanent penetration of the pile or set into the ground. Thus, the maximum bearing capacity of the pile can be determined immedi ately, and thus eliminate the costly dead load bearing test. Moreover, costly overdriving of the pile may also be minimized and pile tip damage reduced.

It is also an object of the invention to provide a drive cap for aligning the head of the pile with the hammer which embodies a liquid cooled elastomer cushion so that pile head damage is reduced to a very minimum while driving the pile. Internal heat generated by the hysteresis of the elastomer cushion due to the continuous pounding is dissipated and will therefore prevent damage to the pad from burning or charring as well as affording greater endurance thereof and providing a more efficient cushioning effect.

Another object of this invention is to provide a drive cap with means for sensing the force of each hammer blow and displaying the force in the cab and to the operator in order that he may control each impact force whereby they will not exceed the elastic limit of the pile material. thereby preventing permanent damage to the pile.

Still another object of this invention is to provide a means whereby the operator in the cab of the pile driver may determine the maximum bearing load that the pile will support without the need for a costly dead load bearing test.

Yet another object of this invention is to provide a drive cap which will fit both American style box leads with side rails and European style leads with rails or ways which are customarily provided to the rear of the hammer and cap.

A further object is to provide a cap which will fit a large concrete pile and through the use of adapters can be made to accommodate other types of piles, such as wood, steel, H-beams and steel pipe. The adapter may be so constructed that it may be easily replaced and fastened without disassembly of the cap or its cushion.

Still further objects are to provide a cap with the front and one side shorter, and the back and other side beveled inwardly, so the pile head can be fed or guided into the bottom cavity of the cap easily and to further provide a circular upper cavity with a shallow bottom radius for easy alignment of the pile driver anvil.

Still another object is to provide a cap which includes two cushions, one of which receives the impact of the hammer and the other the impact of the pile, with each cushion being water cooled.

These and other objects of the invention will become more apparent from a reading of the following specifi cation taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a top plan view of the drive head with the chambers therewithin for circulation of the coolant being depicted in phantom lines;

FIG. 2 is a front elevational view with portions of the cap cutaway to show the configuration of the head as well as the position of the elastomeric cushion;

FIG. 3 is a view looking into the right side of the drawing shown in FIG. 2 with portions cutaway to show the water circulation between the chamber and the elastomeric cushion;

FIG. 4 is a top plan view of the liquid cooled elasto mer transducer cushion;

FIG. 5 is an elevational view, partially in section, of the transducer cushion;

FIG. 6 is a schematic of the electrical circuitry required to read the force of the hammer blows;

FIG. 7 is a sectional view of a further embodiment of the water-cooled drive cap looking down into the water-cooled chambers;

FIG. 8 is a cross-sectional view on line 88 of FIG. 7.

FIG. 9 is a top plan view of a further embodiment of the elastomeric cushion; and

FIG. 10 shows the cushion partly in elevation and partly in cross section on line AA of FIG. 9.

DESCRIPTION OF THE EMBODIMENTS Turning now to FIG. 1, there is shown a top plan view of the drive cap 10 which comprises an integral cast or forged body portion of substantially rectangular shape having guide lugs ll-l1 offstanding diametrically from the opposite sides thereof. these lugs being adapted to be complemental to American leads. The planar guide lugs 12-l2, which offstand laterally from the rear wall, are arranged to be complemental to European leads. The upper portion of the cap is provided with a circular cavity 13 and includes a concave face 14 which is more clearly shown in FIG. 2, and is adapted to align and hold the hammer anvil on the driving axis.

Referring at this time to FIG. 3 and more particularly to the cross-sectional area to the right of this view, there is shown at 15 a portion of a water or other suitable heat transmitting liquid reservoir which constitutes a head member with the fill means therefor being shown at 16.

In this view are also clearly shown means defining perforations at 17 and 18 which are provided in the inner wall of the reservoir, as at 19, and which will serve to provide for circulation of the coolant through the perforations 20 in the segmentally arranged wall portions 22. This is best shown in FIG. 1.

As is also well shown in FIG. 3, there is illustrated at 23 an upper planar wall, the inner portion of which forms the top of the aforesaid liquid filled chamber, on the concave exterior portion of which the pile driver is adapted to be received and lying in a plane parallel therewith, and therebeneath is the perforate bottom wall 24 of the chamber with the perforations therein being indicated at 25. With further reference to this view there is also shown at 26 an adapter which is only representative of one type of adapter that is available, the perimeter thereof conforming to the interior of the head with its upper surface being flat for a purpose that will now be described, and its lower surface being formed complementally to receive the upper planar surface of the particular type of pile to be driven, this pile being shown in phantom lines at P. The perimeter of the adapter is provided with means defining openings in the wall thereof, as at 34, and these are aligned with perforations 35 in the housing 10 so that suitable cable means may be availed of to secure the adapter to the head.

The elastomer cushion, which constitutes the pri mary inventive concept of this invention, is well shown in the top plan view in FIG. 4; however, it is believed that its cooperation with the elements comprising the drive cap will be best understood by a further study of FIG. 3. In this view it will be observed that the elastomer cushion 27 is provided with a channel 28 which lies directly beneath the perforate area of the wall 24.

It is believed that from a study of this view it will be appreciated that as a hammer blow is applied, the clastomeric cushion 27 is squeezed together causing the liquid which is in groove 28 to rush up into the chamber thereabove and then flow back again to the cushion as the hammer is lifted, thus giving a rapid circulation or agitation of the liquid within the reservoir, thus transferring the heat due to hysteresis in the cushion to the outer walls of the head where it is lost by convection and radiation. In the present drawings though the only cooling is accomplished within the head 10, it will be obvious to those skilled in the art that for heavy loadings where heat generation is high. fins may be added to the exterior of the head to increase the cooling area and in addition the liquid may be circulated through the head from a heat exchanger.

By now referring to the view of FIG. 4, it will be noted that the channel 28 follows a more or less tortuous path which includes an inner end that terminates substantially in the center of the cushion at 29 while the outer end of the channel terminates adjacent to one edge of the pad at 30. The entire outer side wall area of the cushion is provided at the upper edge portion with an outwardly extending lip 31 which, it will be apparent from an examination of FIG. 3, forms a liquid seal to prevent the coolant medium from escaping from the channel area and leaking about the inner wall 19 fo the reservoir. This is best understood by reverting to FIG. 3, the cross-sectional view showing the elastomer cushion in position between the wall 24 and the adapter 26.

With further reference to FIG. 3, it will be noted that there is cast into the elastomer cushion 27, a capacitance transducer that can serve, together with a current amplifier and an oscillograph, to measure the impact blow of the hammer on the head of the pile, as will now be explained in more detail.

Turning now to FIGv 6, there are shown schematically therein plates 34a and 35a ofa capacitor 40 which represents the wire mesh screens which are encapsulated within the elastomeric cushion 27. In parallel with the capacitor 40, between points 41 and 42, there is a voltage source 43 in series with a high resistance 44 limiting the ability of the voltage source 43 to rapidly charge the capacitor. The leads from the two mesh screens 34a and 350 are arranged as shown in FIG. 2 to extend out of one side of the cushion and pass through insulated bushings 28a which are provided in the head 10.

Initially, the wire screens 34a and 35a in the elastomeric cushion 27 are connected to the voltage source 43 through resistor 44 and current flows until the plates are charged and the potential across the plates equals that of the voltage source.

When the hammer strikes the cap, the elastomeric cushion 27 is squeezed together between the bottom surface of plate 24 and the adapter cap 26, thus causing the initial encapsulated point of separation between the wire mesh screen capacitor plates 34a and 35a to be reduced. The capacitor thereby attains an excess charge which starts to bleed off. When the elastomeric cushion 27 springs back to shape upon the hammer being lifted away from the surface 14, the separation of the plates 34a and 35a is suddenly increased and the capacitor thereupon being lacking in its charge, attempts to draw current through resistor 44. Since the resistor 44 is large, it creates a voltage drop and instantaneously causes a voltage drop across the plates 34a and 35a, as well as points 41 and 42. This voltage is then applied to the terminals 48 and 49 of high persistance screen oscilloscope 53 through wires 45 and 46 and can be interpreted in terms of peak force since the squeezing of the elastomeric cushion 27 is proportional to the force of the hammer and therefore the plate separation is proportional to the force of the hammer. Depending upon the specific parameters of the plate size, separation and voltage for a particular method, an amplifier 47 may be required and this is shown in phantom ahead of the oscilloscope input terminals.

It will be recognized by those skilled in the art that there are many other known ways of detecting and displaying a change in capacitance, for example, through more sophisticated systems detecting frequency changes in the tank circuit of which the wire mesh screens 34a and 350 are a part.

By the interpretation of peak force, the operator can adjust the hammer blows so that the elastic limit of the pile head is not exceeded, thereby eliminating damage to the head.

Secondly, the system can be used to determine the static bearing load on a pile after it is driven. By reducing the blow force of the hammer to an amount where the pile ceases to make any further penetration, the force level can be recorded which will be the maximum bearing capacity of the pile, thus eliminating the need of a separate dead load hearing test.

With reference at this time to FIG. 7, there are clearly shown in this view the American and European style leads 75 and 76, respectively, the purpose of which was explained earlier herein,

Also, illustrated in this cross-sectional view are a plurality of chambers 77, each of which is interconnected by means of perforations 78 and by means of which coolant from the surrounding compartments 79 (best seen in FIG. 8) is arranged to circulate through the annular cell 80 and thereafter traverse by way of perforations 81 in the spaced walls 82 and 83 and thereby be brought into communication with the opposed channelized areas 84 and 85, respectively, of the elastomeric cushions 86 and 87.

As described earlier in connection with the electrical transducer concept, as well shown in FIGS. 4 and 5, which constitutes the first embodiment of this invention, reference is made at this time to the pneumatic impact transducer illustrated in FIGS. 9 and 10.

As shown in the plan view of FIG. 9, the elastomeric cushion 87 includes a water coolant channel area 85 such as that described earlier relative to FIGS, 4 and 5, this being illustrated clearly in this view. In addition thereto, as illustrated in dotted outline in this figure, there is provided a circuitous path 88 into which air pressure is introduced.

In view of the detailed description of the first embodiment of this invention, which clearly sets out how the electrical transducer is arranged to function, it would appear sufficient to indicate that as the cushion 87 of this later embodiment is depressed by the impact force of the hammer against the cushion and thereinto the metallic drive cap, that the circuitous cavity is flattened sufficiently to cause the air contained therein to be expelled or discharged into a pressure gauge which is mounted in a clear view position in front of the ham mer operator in the cab of the machine.

It will be understood from the earlier description of FIGS. 4 and 5 that here also as the hammer is lifted and lowered in this embodiment of the invention, the air which travels to and from the pressure gauge will provide a clear indication to the operator not only of the condition of the hammer but also the pile being driven.

In the earlier embodiment of the drive head, the circular cavity 13 was shallow as is best shown in FIGS. 2 and 3. However, by reason of the fact that in the second embodiment the elastomeric cushion 86 is positioned in the cavity 90 in the head, the walls thereof must necessarily be higher to receive both the elastomeric cushion and the hammer.

The perimeter of the elastomeric cushion 87, which is positioned between the pile and the wall 83 of the head, is designed to be received snugly within the smooth surface area 91 of the drive cap and is arranged so that when the cushion is in its relaxed condition, water pressure can be emitted from the chambers 77 into the cushion without developing any leakage between the perimeter of the cushion 87 and the surface area 91.

The invention disclosed hereinbefore illustrates several commercial embodiments of this invention, but the structure may be modified or changed while still maintaining the true intent of the invention as hereinafter defined and claimed.

That which is claimed is:

l. A drive cap for a pile driving machine comprising, in combination: a body portion including a plurality of intercommunicating liquid cooled chambers, parallel spaced walls forming at least portions of one of said chambers, one of said parallel spaced walls forming a support surface, a removable adapter means arranged to be seated over a pile member and a resilient, impact block of elastomer material interposed between said support surface and said adapter means for transmitting force to the top of the pile member.

2. A drive cap for a pile driving machine as claimed in claim 1, wherein another of said spaced walls includes means defining openings therein.

3. A drive cap for a pile driving machine as claimed in claim 2, wherein said resilient, impact block of elastomer material includes channel means whereby liquid may traverse between said chambers and said resilient, impact block of elastomer material to cool the latter.

4. A drive cap for a pile driving machine as claimed in claim 1, wherein the body portion includes plural guide means offstanding laterally therefrom whereby said drive cap is adaptable to varying types of leads.

5. A drive cap as claimed in claim I, wherein said body portion includes an enclosed space for containing a supply of said cooling liquid.

6. A drive cap for receiving blows and transmitting them to the top of a pile comprising a body portion having a recess and a resilient, impact block of elastomer material positioned in said recess, said block being positioned in the line of force transmission of said blows to the pile when said cap is positioned on top of a pile, means for cooling said block comprising a passage for cooling liquid positioned in the body of said block, and wherein said body portion includes an enclosed space for containing a supply of said cooling liquid, further including a wall separating said enclosed space from said resilient, impact block, and a perforation in said wall connecting said passage to said space for flow of said liquid.

7. A drive cap as claimed in claim 6, wherein said space is bounded by a second wall which is vertically spaced from said first mentioned wall and is substantially parallel thereto, each of said walls extending horizontally and being adapted to transmit the force of said blows to said pile, and partition walls connect said first and second walls to form a plurality of chambers between said first and second walls, perforations in said partitions providing for circulation of said cooling liquid between said chambers.

8. A drive cap as claimed in claim 7, wherein said passage in said cushion is of generally spiral form and a plurality of perforations connect said passage to said chambers.

9. A drive cap as claimed in claim 6, wherein said body portion has pairs of guide lugs outstanding therefrom at different locations and of different shapes to adapt said drive cap for use with leads of different types.

* i i i t 

1. A drive cap for a pile driving machine comprising, in combination: a body portion including a plurality of intercommunicating liquid cooled chambers, parallel spaced walls forming at least portions of one of said chambers, one of said parallel spaced walls forming a support surface, a removable adapter means arranged to be seated over a pile member and a resilient, impact block of elastomer material interposed between said support surface and said adapter means for transmitting force to the top of the pile member.
 2. A drive cap for a pile driving machine as claimed in claim 1, wherein another of said spaced walls includes means defining openings therein.
 3. A drive cap for a pile driving machine as claimed in claim 2, wherein said resilient, impact block of elastomer material includes channel means whereby liquid may traverse between said chambers and said resilient, impact block of elastomer material to cool the latter.
 4. A drive cap for a pile driving machine as claimed in claim 1, wherein the body portion includes plural guide means offstanding laterally therefrom whereby said drive cap is adaptable to varying types of leads.
 5. A drive cap as claimed in claim 1, wherein said body portion includes an enclosed space for containing a supply of said cooling liquid.
 6. A drive cap for receiving blows and transmitting them to the top of a pile comprising a body portion having a recess and a resilient, impact block of elastomer material positioned in said recess, said block being positioned in the line of force transmission of said blows to the pile when said cap is positioned on top of a pile, means for cooling said block comprising a passage for cooling liquid positioned in the body of said block, and wherein said body portion includes an enclosed space for containing a supply of said cooling liquid, further including a wall separating said enclosed space from said resilient, impact block, and a perforation in said wall connecting said passage to said space for flow of said liquid.
 7. A drive cap as claimed in claim 6, wherein said space is bounded by a second wall which is vertically spaced from said first mentioned wall and is substantially parallel thereto, each of said walls extending horizontally and being adapted to transmit the force of said blows to said pile, and partition walls connect said first and second walls to form a plurality of chambers between said first and second walls, perforations in said partitions providing for circulation of said cooling liquid between said chambers.
 8. A drive cap as claimed in claim 7, wherein said passage in said cushion is of generally spiral form and a plurality of perforations connect said passage to said chambers.
 9. A drive cap as claimed in claim 6, wherein said body portion has pairs of guide lugs outstanding therefrom at different locations and of different shapes to adapt said drive cap for use with leads of different types. 